Automatic station



Dec. 27, 1927.

s. e. L E QNARD AUTOMQTIC STATION Filed Dec. 1925 2 Sheets-Sheet 1 Fig.1.

WITNESSES: lNVENTOR y' 5 Stuart G'Leonard :1 i 4 BY 6 i A'TTORNEY Dec. 27, 1927. 1,654,505

5. G. LEONARD AUTOMATIC STATION Filed Dec. 29, 1925 2 Sheets-Sheet 2 Fig.2.

WITNESSES: 5 INVENTOR JzfuarZGLeonard I y A'TTORNEY Patented Dec. 27, 1927.

'UNITED STATES PATENT. OFFICE.

ssuance s. LEONARD, or naxnwoon, 1110, assrenon 'ro wns'rmenonsn ELECTRIC &

manuracrunrne COMPANY, A GORPORATIQN or PENNSYLVANIA."

AUTOMATIC sra'rion.

Application filed December 29, 1925, Serial No. 78,165.

My invention relates to automatic stations and more particularly to stations comprising a plurality of electrical translating devices l'or supplying energy to a common consummg circuit.

An object oi my invention is to provide means for limiting the amount 01' energy that may be supplied to the Consuming circuit by any one translating device and means for simultaneously controlling the effectiveness of the load-limiting means of all of the translating devices thatare operating in a station, in such manner that the total load will be distributed between the several opratio- My invention comprises in general, an electrical translating station including two or more electrical translating devices adapted to supply energy to acommon consuming circuit. A plurality of load-limiting resis tors are connected between each of the translating devices and the consuming circuit and means are provided for short-circuiting the resistors under normal operating conditions. A common means is provided for controlling the operation of all of the resistor short circuiting means of the several translating devices simultaneously. This means comprises, in its preferred form, an electro'pneumatically operated contact drum that may be caused to turn in either direction to open or close corresponding resistor short circuiting means of all of the operating translating devices simultaneously.

A plurality of load-responsive devices are associated with the several translating de- Jices and are adapted to control the operation of the contact drum in such manner that when any one of the translating devices is traversed by current in excess of a. predetermined value the contact drum open-circuits corresponding resistor short-circuiting means of all oi? the operating trzinslating devices to decrease the amount of energy that is supplied to the consuming circuit. \Vhen all of the translating devices are traversed by current of less than a predetermined value, the load-responsive devices cause the drum to turn in the opposite direction to close the resistor short-circuiting means of the several translating devices simultaneously, thereby permitting the translating devices to supply a greater amount of energy to the consuming circuit.

' crating devices equally or in a predetermined By providing means of the above indicated character tor eli'ecting simultaneous operation of the load-limiting means of the several translating devices in a station, unequal distribution of load between the several devices which is undesirable and which may be injurious to the devices, is precluded.

In the accompanying drawings,

Figure 1 is a diagrammatic representation of an electrical system embodying my invention, includingpower apparatus and circuits and auxiliary apparatus and circuits for controlling the power apparatus,

Fig. 2 is a schematic representation of the power apparatus and circuits shown in Fi 1, and

Fig. 3 is a schematic representation of the auxiliary or control apparatus and circuits shown in Fig. 1.

Like reference characters in the different figures indicate like pieces of apparatus.

Referring to the drawings, two electrical translating devices 1 and 2 are adapted to supply energy to a common consuming cirlcuit The translating devices 1 and 2 are illustrated as rotary converters receiving energy from supply circuits 4 and 5, respectively. It will be understood that the circuits 4 and 5 may be connected to the same supply system through proper transformers, starting and running circuit interrupters, and such other devices as may be necessary or desirable.

My invention-is particularly adapted to be utilizedin a station in which the translating devices are automatically controlled, but since the automatic controlling devices do not constitute an integral part of my invention, and since such devices are now well known in the automatic station art, they are not shown or described in this application.

One of the direct-current terminals of the converter 1 is connected through a series field-magnet winding and an inter-pole fieldmagnet winding to earth. An equalizer con tactor 6 is connected from the point between the series field-magnet winding and the interpole field-magnet winding to an equalizer bus conductor 7. The other direct current termiaial of the converter 1 is connected through a plurality .ofresistors 8, 9 and 10 and a circuit interrupter 11 to the consuming circuit 3.

Circuit interrupters 12, 13 and 1 are provided for varying the effectiveness of the resistors 8, 9 and 10. The circuit interill rupters 12, 18 and 1.4L are so connected with respectto the resistors 8, 9 and 1.0 that when all of these circuit interrupters are open, all oi the resistors are connected in series; when the circuit interrui itcr closed and the circuit interrupt'ers 12) and, ll: are open, the resistors 9 and 10 are shortcircuited and only the resistor 8 is e'lifective; when the circuit interrupters 12 and 1.3 are closed and the circuit interrupter ll is open, the resistors 8, 9 and 1.0 are connected in parallel relation to each other; and when the circuit interrupter 14: is closed, all of the resistors 8, 9 and 10 are sl'iort-circnited and, therefore, inetlecti ve.

A drum men'iher 1.5 is provided with conact segments 1o, l7. l8 and 19 and contact mgers 20 to 31, inclusive, which cooperate o control. the operation of the circuit interrupters i1, l3 and let that are associated with the converter 1, and corresponding circuit interrupters associated with the converter 2, which will he described presently. The drum member 15 is mounted on a shaft 32 to which a worm wheel or spiral gear wheel is secured. The wheel 38 is engaged by a worm or spiral pinion gear 34: that is mounted on a shaft A pinion gear 36 is also mounted on the shaft and meshes with a rack memher 37 that is secured to a piston rod 38. The rod 38 is provided with pistons 39 and it) at opposite ends thereof. "he pistons 39 and it) are encased by opposite ends of a cylinder 41.

Valves 42 and are adapted to control the admission of air or other operating fluid from supply pipes or conduits l l and to the respectiie ends of the cylinder -1ll. The valve 4-2 is provided with a stem 16 and a housing 41-7. A. pin 41-8 is secured to the valve stem sit and engages one end. oi? a compression spring til), the, other end. of which engages the valve housing 457 in ich manner that the valve 1-2 is normally held out oi engagement with its seat, thereby permitting pressure to he applied to the pis ton 3t) :t'rom the supply pipe or conduit 44:. A magnet coil co-operatcs with a magnetic core member 51. that is secured to the upper end of the valve stem l-G in such manner that when the coil Stl is energized the core member 51. is actuated. downwardly to close the valve 42 against the pressure of the spring 19.

The valve is provided with a stem 52 and a. housing A pin M is secured to the stem 52 and engages one end of a compression spring 55, the other end of which engages the housing 53. Thus, it will be seen that the valve l?) controlled hy the spring 55 in a similar manner to that in which the valve 42 is controlled by the spring 4L9, but that the spring 55 normally maintains the valve in engagement wit-l:

its scat whereas the spring 49 normally maintains the valve 42 out ot engagement with its seat. The upper end oi? the valve stem 52 is provided with a magnetic core niemlier 5G with which a magnet coil 57 is adapted to co-operate. hen the magnet coil 57 is energized, the core inemher 56 is actuated upwardly, thereby opening the 'alve ell-3 against the presure oi the spring to admit 0] rating fluid from the supply pipe or conduitis to the right hand end. of the cylinder member l-l.

From the foregoing description of the actuating means of the drum memher 15, it will he seen that when both the magnet coils 50 and 51 are (lo-energized, the valve 42 is open and the valve 43 closed. Therefore, tluid pressure is applied to the piston 39 but no pressure is applied to the piston eltl. The 'stons 3!) and 4-0 and the rod 138 are, therefore actuated to the. extreme right-hand position, as shown in the drawing, and; the drum member 15 turned to the posit-ion shown in the drawing by means ot the rack 37, the pinion gear 2-56, the shaft -35, the worm or spiral pinion gear Set, the worm wheel or spiral gear wheel 33 and the shaft 32.

When hoth the magnet coils 50 and 57 are energized, the valve 42 is closed and the valve 41-3 is open, thereby relieving the pressure on the piston 39 and applying pres sure to the piston 4.0. The pistons 2-39 and ii), the rod 38 and the rack 37 are thercupon actuated to their extreme left-hand position, thereby turning the drum menihcr iii in such manner that the contact fingers 20 to 31, inclusive, successively engage or disengage the contact segments 1(3, 17, 18 and 19 in the positions indicated by the lfOlttl] lines ll, Ill. and IV in the drawings.

When the magnet coil 50 energized and the magnet coil 57 is (lo-energized, hoth the are closed and no pressure valves 42 and 41- is applied to either oi? the pistons 39 and 4-0. Therefore, the pistons 35,) and elf) remain stationary in whatever position they o cupy, and the drum member 15 likewise re mains stationary. until the magnet coil is? is energized or the magnet coil 50 is deenergized.

The energization oi' the magnet coils fill and 5? is controlled liy overload relays as and 59 that are associated with the sup y circuit 1- ol the converter 1 through he agency of a current transtormer (it), and overload relays 1 and (52 that are associated with a supply circuit 5 oi the converter 2 through the agency ot a current transformer (Si-3. Each of the overload rclays 58, 59, ill and (i2 is provided with a single switch that is closed except when the associated current transformer, and hence the relay operating coils, are trav ersed hy current in excess of a predeterminel value. caused by an excessive current.

ill)

7 bus conductor 7. V

circuit interrupters7 8, 7 9, S and 81 are as-.

"Mm va i a-.

traversal ol the supply circuits 4 and 5. The switches of the overload relays are adapted to connect the magnet coils 50 and 57 between the terminals of a battery or other source of energy 6% under predetermined conditions.

The battery 64 is also adapted to supply energy for the operation of the circuit interrupters 11, 12, 13 and 14 through operating magnet coils 65, 66, 67 and 68, respectively. The energization of the coils 65, 66, 67 and 68 is controlled by the contact drum and by an auxilary switch 69 of the equalizer contact (3, auxiliary switches 70 and 71 of the circuit interrupter 11, an auxiliary switch 72 of. the circuit interrupter 12 and an auxiliary switch 73 of the circuit interrupter 13, each of these auxiliary switches being closed when the contactor or circuit interrupter with which it is associated is closed.

The converter 2 is provided with an equal. izer contactor 7 4- corresponding to the equal,- ize r contactor 6 of the converter 1 and connected in the same manner to the equalizer Resistors75, 76 and 77 and sociated with the converter 2 in the same manner that resistors 8, 9 and 10 and circuit interrupter-s 1.1, 12, 13 and 14:, respectively, are associated with the converter 1. Circuit interruptcrs 78, 79, S0 and 81 are provided with operating magnet coils 82, 83, S4 and 85, respectively; An auxiliary switch 86 of the equalizer contactor 74-, auxiliary switches 87 and 88 ot the circuit interrupter 78, an auxiliary switch 89 of the circuit interrupter 79 and an auxiliary switch 90 of the circuit in terrupter 80 are connected in the same manobjects.

ner as the corresponding auxiliary switches of the equalizer contactor 6 and the circuit in terrupters 11, 12, 13 and 14 that are associated with the converter 1.

Having thus described the apparatus and circuits of the system embodying my invention, I will now describe the method in which the systemoperates to accomplish the desired Assuming that both the converters 1 and 2 are at rest and that conditions have arisen in response to which it is desired that one of the converters be started, converter 1 may be started andbrought up to the proper speed and voltage with the correct polarity by any suitable means well known in the art. hen this condition is obtained, the first step preliminary to connecting the converter 1 to the circuit 3 is the closing of the equalizer contactor (3, which is accomplished by energizing its operating coil in any suitable manner.

Then the equalizer contactor 6 is closed its auxiliary switch 69 is also closed to complete a circuit from the upper terminal of the battery 64, through the-switch 69, the operating coil of the circuit interrupter 11, the contact finger 27, contactor segment 18 and contact linger 26 of the contact drum 15, to thelower terminal of the battery 64L. The coil 65 is thus energized; to eii ect closing of the circuit interrupter 11, which connects the direct-current end of the converter 1 to the circuit 3 through the resistors 8, 9 and 10 in series. The converter 1 will then supply energy to the circuit 3 through the resistors 8, 9 and 10.

It the load assumed by the converter 1 when the circuit interrupter 11 is closed is excessive, the current tl'ilIlSfOll'IlQl (30 will be siuliciently energized, by reason of the excessive current traversing the supply circuit 4, to energizethe overload relay to such a degree that it will open its switch. The overload relay 59 may also be energized sufliciently to open its switch, but since the switches of the relays 58 end 59 must both be closed before the next step in the sequence of operation can take place, the opening of the switch 59 has no further effect than the opening of the switch 58. The relay 59 is calibrated to operate at a higher current value than is the relay 58, for a purpose which will be hereafter set forth.

hen the amount-of energy supplied to the circuit 3 by the converter 1 has decreased to a predetermined value, both of the overload relays 58 and 59 will be permitted to close their switches. hen these switches are closed, a circuit is established from the upper terminal of the battery 64:, through the auxiliary switch 71 of the circuit interrupter 11, which was closed when the circuit interrupter 11 closed; the switch of the overload relay 62 that is associated with the supply circuit 5 and is de-energizedbecause the converter 2 is not operating; the switch of the relay 59; and the magnet coil 50 that is associated with the operating mechanism of the contact drum 15, to the lower terminal of the battery 64. The magnet coil 50 is thus energized to close-the valve 12, thereby relieving the pressure on the piston 39. At the same time, the magnet coil 57 is energized by means of a circuit extending from the upper terminal of the battery (54L through the auxiliary switch 71 ot the circuit interrupter 11, the switcl'ies of the overload relays (32, 59, 58 and 61 in series, the coil 57, and the contact finger 20, cdn tact segment 16 and contact linger 21 of the contact drum 15, to the lower terminal of the battery G-l.

\Vhen the magnet coil 57 is thus ener gized, it eii'ects opening of the valve -13, which then admits air to create pressure on the piston 40 in the right-hand end of the cylinder 11. The pistons 39 and to are, therefore, moved to the left to turn the contact drum 15 in such manner that the position indicated by the broken line 11 coincides with the line of the contact fingers.

In position II of the contact drum the contact segment 1.8 is out of engagement with the lingers 26 anti 2?, hut the circuit of the operating coil (S5 of the circuit inter rupter 11 is not open, since the auxiliary switch 70 of the circuit interrupter 1.1 is connected in parrallel relation to the contact lingers 2c and 27 to constitute a holding circuit for the coil (35. When the contra drum is in position H, a circuit is completed horn the upper terminal ot the hattery (lei: throrurh the auxiliary switch (39 of the equalizer contactor (i, thi contact linger E22, :outuct segment 17, contact linger operating coil 66 of the circuit interrupter 1E3, arul au1 iliar switch 70 ot the circuit interrupter 1 l to the lower terminal of the hatter (ll. The o' 'ierating coil ('36 is thus energijixeil to close the circuit interrupter 12, which shortcircuits the rci-iistors 9 aml l0 aiul leaves only the resistor 8 in circuit he tween the converter l, and the circuit 1;).

ll. the (increased rcsis-stam-e hctwecn the converter anil the consumin circuit permits an excessive current to traverse the converter, the overload relay will open its switch to interrupt the circuit ot the magnet oil 57. The valve 4:3 is, therefore, closed to relieve the pressure on the piston l0, and the n'iovenient ot the pistons and the con tact drum is stopped. Assuming that the loacl is not excessive, however, he switches of the overload relays will remuin closed the euergzation of the magnet coils in. 57 will he maintained and the contact lrum 1.5 will he so turnetl that it will he ei'igu ged hy the contact lingers in the positions in- (tlicuterl hy the broken line iln this position a circuit is completed from the up per terminal of the hattery (Sslthrough the auxiliary switch (if) of the equalizer routactor (3, the contact linger 22, contact segrment 1? antl contact linger 2-2: of the contact ilruni 15, the auxiliary switch TL of the circuit interrupter 12, which ras closeil when the circuit interrupter l2 closetl, autl the operating; coil 6? of the circuit inter- TUPi O/I. 13 to the lower tern'iinal ot the hattery 64L.

.Vi hen the operating; coil ()7 is thus enerfl'lZQth the circuit interrupter 153 is closetl to connect the resistors 5%, l) unil ll) in pr rallel relation to each othe hetwcen the t'i 1- \crlcr 1 anti the circuit. The resistance of this circuit is thus l'urther (lei-reared permit, the converter 1, lo supply more en one) to the circuit Il. it this amount ct energy is not erxcessiw, the OVOllOiltl switches will remain closeil and, the contact lru1n 13 will he turneil so tl at position 1 coincules with the :ontact lingers. in this position a circuit is estaa ishetl from tne upper terminal of the l utter; G it through the au. ;'lia- 'y switch (39 oil the equalizer contactor the contactlinger 22, t cc uct segment 1."? and the contact linger 25 o the contact rlruiu '15, the auxiliary switcr of the circuit intcrru ii'ler iii-l, which was cloretl when the circuit intc iu'iicr l cl: seal,

and the operating coil (38 ;l terru )i' 1 i it to the lower terminal ot the 3. position .lii ot the contact (lruu'i the couta't uenl: 1c is out of cngagg en'icnt "w th the con act lin ljers 2t) uul it l the circuit of the magnet coil .3? is thei. by intcrrupteil to permit the valve ill-5 to he closed. Thus. when the p itou {it has hccu ctual'eil 2.. to its extreme lei haiul position the press. re thereon is relievetl.

'ihe converter l is now normally coun-eclcil hctwccu the supply circuit l anrl the consuming circuit 23 to translate energy thcrclictvvccu. l'rhcn it is (lCHll'Otl that the converter 2 he sturtcd to o im'ate in parallel relation to the converter 1, its operation may he star-toil in the same manner as tlescriheal with. re pect to the converter 1. The same operations will then take place up to anil in- Cllltllil tl' the closing; of the equalizer contactor 7% which corresponds to the equalizer coiitaetor G of the converter 1. lVhcn the equalizer eontactor 741: is closet l, its auxiliary switch 86 is also el0se l to complete the ener- Zing circuit ht the operzu ing coil 82 ot the circuit interrupter 78. This circuit cxtenils from the upper terminal oi the hi ttery (it, through the switch the coil, and the oo, auxiliary switch of the circuit interrupter 11. to the lover terminal ol the The circuit interrupter 78 thus closed. to connect the converter 2 to the circuit 3 througzjh the resistors 75, T6 i illl 77. it the load supplied by "he coi'n'erlcr 2 to the circuit 3 through the resistors 75, To un l 77, when the circuit llltci'illlj)t(3l' it is closed, is not excessive, the switches of the UYClli'ultl relays (31 and. (32 will not he opened. The circuit oil. the magnet coil :30 will, therefore, not he i111 erruptetl and the valve 42 will. remain eloseil to permit the pistons 3S) andv ill to remain in the extreme lflihllulltl position anil to permit the contact ih'uui 15 to remain in position ll". the opera-ling V- the circuu o: coil 82% ot the circuit uilcrrupl'ers 7 will,

lhere'lfori-i he complclcil 'l'rorn the upper terminal oi: the battery (ll, through the auxilmry switch 86 ot the equalizer ('onl'mflol 74-, the contact linger 28 couuiilete the circuit oil the operatiiu coil Q i ii contact; scgxuicut l9 ha i lie ry (i l-v.

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of the circuit interrupter. 80, which extends from the upper terminal of the battery 64, through the auxiliary switch 86 of the equalizer contact 74;. the contact finger 28, contact segment 19 and contact finger 30 of the contact drum 15; the auxiliary switch 80 of the circuit interrupter 79; and the operating coil Set of the circuit interrupter 80, to the lower terminal of the battery 64. The operating coil 84 is thus energized to effect closing of the circuit interrupter 80 and the auxiliary switch 90 thereof, which completes the circuit of the operating coil 85 of the circuit interrupter 81. v

This circuit extends from the upper terminal of the battery 64-, through the auxiliary switch 86 oi? the equalizer contactor 74;

the contact fin er 28 contact se ment 19 and contact finger 31 oft-he contact drums 15 the auxiliary switch 90 of the circuit inter rupter 80; and the operating coil 850i the circuit interrupter 81 to the lower terminal of the battery 64. The circuit interrupter 81 is thereupon closed to connect the con verter 2, directly tothe circuit 3 to supply energy thereto in parallel relation to the converter- 1.

While the converters 1 and 2 are operating in parallel relation, an excessive current traversal of either of the-supply circuits 4t and 5 will cause the corresponding overload relay 59 or 62 to open its switch, thereby interrupting the-energizing circuit of the mag net coil 50 to permit the valve 42 to open. Since the valve 43 is closed, as previously set forth, there is no pressure on the piston and the pressure applied to the piston 39 by reason of the opening of the valvefll2 causes the pistons 39 and to be moved to the right, thereby turning the contact drum 15 back to-position III. In this position, the circuits of the operating coils 68 and 85 of the circuit interrupters 14 and 81 respectively, re interrupted to permit these circuit interru iiters to open. Thus, one step of resistance is inserted between each of the converters and the coi'isuming circuit 3 to decrease the amount of energy supplied by each converter. As long as the overload conditions persist in either converter, the lmckward movement of the drum 15 will be eoiitinued to increase the amount ot-resistance that is connected between each converter and the circuit 3.

Each time that the drum moves to a new position, the corresponding resistor shortcircuiting circuit interrupters of the two converters are opened simultaneously, so that the relative value of resistance connected between each converter and the consuming circuit is always the same or, if the converters are of different capacities, in a predetermined ratio. The ratio of load distribution between the two converters is, therefore, unchanged by the operation oi of either of the relays 59 or the load-limitingmeans. In like manner,

when the overload conditions no longer -X1S1J,tll6 load-limiting resistors of the two '59 and 62. It isclear from theforegoing of the switch 62 causes. the contact drum 15 to be turned in the reverse direction, while the opening of the switch of either of the relays W or or, while the description that the opening 00 switches of the relays 5S) and (52 remain closed, only stops the operation of the contact drum and permits it to remain in whatever position it has assumed.

By means of the relative calibration of the overload relays, therefore, a certain degree of'overload will simply stop the oper ation of the drumwhile a greater degree of overload will cause the drum to return in the reverse direction. For example, a current traversal of either-of the circuits 4; and 5 of 1,000 amperes may cause the drum 15 to turn in the backward direction, but upon the insertion ofone step of resistance between each of the converters and the consuming circuit, the consequent reduction 01" current will not necessarily cause the drum to move forward again unless the current is reduced below the operating value of the relays 58 and 61, which may be 7 amperes. Thus, as long as the value of current is between the settings of the relays P58 and 59 or 61 and 62the drum will remain stationary.

It is obvious that the contact drum-15 may be provided with as many contact segments similar to the segments 17 and 19 as there are translating devices in'the station to becontrolled, and that all of the circuits may be extended in such manner that the load-limiting devices of as many translating devices as are desired may be COUt'lfOllGd. by a single contact drum. By this means, the load distribution between any number of translating devices may always be maintained in a constant ratio. It is also clear, that various changes andmodifications may be made in the apparatus and circuits of the system embodying my invention without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. In an electrical translating station, the combination with a. load circuit and a plurality of dynamoelectric machines for supplying energy thereto, of resistance means for connecting each machine to the circuit and means for automatically varying the Hit) the operating machines in a predetermil'ied ratio simultaneously, in accordance with the value of current traversing the operating machines.

2. In an electrical translating station, the combination with a load circuit and a pin-- rality of dynamo-electric machines for sup plying energy thereto, of resistance means for connecting each machine to the circuit and means for automatically varying the effectiveness of the resistance means of all of the operating machines in a predetermined ratio simultaneously, in accordance with the value of current traveming any one of the operating machines.

3. In an electrical translating station, the combination with a load circuit and a plu rality of dynan'io-electric machines for supplying energy thereto, of resistance means for connecting each machine to the circuit and means for automatically varying the effectiveness of the resistance means o'l all of the operating machines equally and simultaneously, in accordance with the value of current traversing the operating machines.

l. In an electrical translating station, the combination with, a load circuit and a plurality of dynamo-electric machines for supplying energy thereto, of resistance means for connecting each machine to the circuit and means for automatically varying the effectiveness of the resistance means of all of the operating machines equally and simultaneously in accordance with the value oi current traversing any one of the operating machines.

5. In an electrical translating station, the combination with a load circuit and a plurality 0t dynamo-electric machines for supplying energy thereto, of a resistor associated with each machine, means for connecting each resistor between the associated machine and the load circuit when the machine is operating, means for short-0ircniting all of the resistors under normal operating 'ii-onditions, and means for open-circuiting the resistor short-circuiting means of all ol': the operating machines simultaneously when any one of the operating machines is traversed by current in excess of a predetermined ralue.

6. In an electrical translating station, the combination with a load circuit and plurality of dynamo-electric machines for supplying energy thereto, of a corresponding set of resistors associated with each machine, means for connecting each of resistors between the associated machine and the load circuit when the machine is op ating, means for short-circuiting all of the resistors under normal opera conditions, and means for open-cireuiting the short-circuiting means ol' corresponding resistors of all oi? the operating machines simultaneously r-xhen any one of the operatng inacl'iincs is traversed by current in excess oi a predetermined value. 7. In an electrical translating station, the combination with a load circuit and a plurality ot dy mini-electric machines for sup plying energy thereto, of a plurality o'li loa llimiting resistors associated with each machine, means for connecting all of the resistors oil each n'nichine in series between the -rachine and the circuit when the machine is operating, means for short-circuiting each of the resistors and means for simultai'iemisly controlling the resistor short-c1rcuitingmeans of all ot the machines comprising an clrazlropneuinatically operated contact drum and a plurality of load-rcsponsiYe devices-z lor controlling the operation oi the drum.

8. In an electrical translating station, the combination with a load circuit and a pluralit-y of dynamo-electric machines tor imp-- plying energy thereto, oil a plurality oil? loadlimiting resistors ai-xsociatcd with each machine, means for connecting ll of the rcsistors of each machine in l etn'cen the machine and the circuit when the machine is operating, means for short-circuiting each oi" the resistors, a contact drum for controlling the operation of all of the resistor short-en cuiting means and means lor so cinitrolliiug; the operation of the contact drum that corresponding resistor short- :ircuiting means cl all of the operating machines are :iimultancously open-clrcuitcil. when any machine is traversed by current in excess of a prcdcteu mined "value andv simultaneously close-circuited when each of the machines is traacrscd by current of less than a prcilctcrminod value.

In testimony whercotl', I have hereunto suhscribed my name this 22 day oi Dew-usher. 19:25 

